Zhou, X-R et al. (Journal of Bacteriology, 181 (14), p. 4342-4352 (1999)) discloses that the protein VirE2, a single-stranded DNA-binding protein of Agrobacterium tumefaciens, can be transferred into a host cell by a tumorigenic Agrobacterium. Zhou et al. disclosed that they were only at amino acid 39 (from the N-terminus, as is customary in the art) able to introduce a heterologous amino acid sequence which was transferred to the host cell. Zhou et al. concluded that it was not practically feasible to base a protein delivery system on fusions at one of the two ends of VirE2. Small proteins at least are tolerated as an insertion at amino acid 39.